Stacking refers to connecting plural devices, e.g., switching devices, via stack ports and configuring the plural devices properly to form a virtualized device. The virtualized device is referred to as a stack (or stacking device, stacking system), and each switching device in a stack is referred to as a member device. A member device may be a chassis-type device, providing a main control board and slots. Each slot can accept an interface board. The port density can be changed by adding interface boards. For example, a switching device serving as a member device may be capable of accepting 6 interface boards, each interface board may include 4 switching chips, and each chip can provide 64 non-aggregated ports. For another example, a switching device serving as a member device may be capable of accepting 16 interface boards, each interface board may include 6 switching chips, and each chip can provide 64 non-aggregated ports. Member devices of a stack may have different capabilities, i.e., having different port density.